The present invention relates to novel enols, their geometric isomers, tautomers and halogen addition products which have herbicidal activity, compositions which contain these compounds as active ingredients and to a method of selectively controlling weeds which comprises the use of the novel compounds or of compositions containing those compounds.
From European Patent application No. 83108306.8, Publication No. 0 104 432, certain styrene derivatives are disclosed as plant growth regulators and herbicides.
The herbicidal effectiveness of a given styrene derivative, however, cannot be predicted from an examination of the substituent groups attached. Frequently, closely related compounds will demonstrate quite different weed control capabilities. Various compounds may overlap or have complimentary areas of activity or selectivity, and therefore, be useful in combination to control a variety of weeds upon application of a single composition.
Furthermore, previously known sytrene derivatives are not completely effective. An ideal herbicide should provide selective weed control over its full growing season with a single administration at low dosages of application. It should be able to control all common weeds by killing them as the seed, the germinating seed, the seedling, and the growing plant. At the same time, the herbicide should not be phytotoxic to the crops to which it is applied and should decompose or otherwise dissipate so as not to poison the soil permanently. The known styrene derivative herbicides fall short of these ideals. It would be desirable to have new herbicides which show even more selective control of undesirable plants among desirable crop plants or which complement the known styrene derivatives in activity.
The compounds of this invention are capable of controlling plants which were not or are not satisfactorily controlled with known compounds. Previously known styrene derivatives are either too aggressive toward sensitive cultivated plants, or, if they are well tolerated are insufficiently active against the weeds to be controlled.
Surprisingly, the active substances according to the present invention are distinguished from the known styrene derivatives by distinctly better tolerance by cultivated plants, (that is to say better selectivity) and by being more active against weeds, particularly preemergence.
Accordingly, one object of the present invention is to provide novel enols which are superior to known compounds of similar structure in respect of their herbicidal action and are better tolerated by important cultivated plants.